There is known a conventional belt-type continuously variable transmission controller in which an actual secondary hydraulic pressure is controlled based on a multiplier of an oscillation component included in the actual secondary hydraulic pressure and an oscillation component included in a variable speed ratio, when performing a belt slip control slipping a belt wound around pulleys at a predetermined slip rate by setting the actual secondary hydraulic pressure to be lower than a hydraulic pressure during a normal control. This eliminates the necessity for directly detecting the belt slip rate and thereby facilitates the belt slip control (see Patent Document 1, for example).